1EXEC(1P) POSIX Programmer's Manual EXEC(1P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 exec — execute commands and open, close, or copy file descriptors
14
16 exec [command [argument...]]
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19 The exec utility shall open, close, and/or copy file descriptors as
20 specified by any redirections as part of the command.
21 If exec is specified without command or arguments, and any file
23 descriptors with numbers greater than 2 are opened with associated re‐
24 direction statements, it is unspecified whether those file descriptors
25 remain open when the shell invokes another utility. Scripts concerned
26 that child shells could misuse open file descriptors can always close
27 them explicitly, as shown in one of the following examples.
28 If exec is specified with command, it shall replace the shell with com‐
30 mand without creating a new process. If arguments are specified, they
31 shall be arguments to command. Redirection affects the current shell
32 execution environment.
33
35 None.
36
38 See the DESCRIPTION.
39
41 Not used.
42
44 None.
45
47 None.
48
50 Default.
51
53 Not used.
54
56 The standard error shall be used only for diagnostic messages.
57
59 None.
60
62 None.
63
65 If command is specified, exec shall not return to the shell; rather,
66 the exit status of the process shall be the exit status of the program
67 implementing command, which overlaid the shell. If command is not
68 found, the exit status shall be 127. If command is found, but it is not
69 an executable utility, the exit status shall be 126. If a redirection
70 error occurs (see Section 2.8.1, Consequences of Shell Errors), the
71 shell shall exit with a value in the range 1−125. Otherwise, exec shall
72 return a zero exit status.
73
75 Default.
76 The following sections are informative.
78
80 None.
81
83 Open readfile as file descriptor 3 for reading:
84 exec 3< readfile
86 Open writefile as file descriptor 4 for writing:
88 exec 4> writefile
90 Make file descriptor 5 a copy of file descriptor 0:
92 exec 5<&0
94 Close file descriptor 3:
96 exec 3<&−
98 Cat the file maggie by replacing the current shell with the cat util‐
100 ity:
101 exec cat maggie
103
105 Most historical implementations were not conformant in that:
106 foo=bar exec cmd
108 did not pass foo to cmd.
110
112 None.
113
115 Section 2.14, Special Built-In Utilities
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118 Portions of this text are reprinted and reproduced in electronic form
119 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
120 -- Portable Operating System Interface (POSIX), The Open Group Base
121 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
122 cal and Electronics Engineers, Inc and The Open Group. (This is
123 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
124 event of any discrepancy between this version and the original IEEE and
125 The Open Group Standard, the original IEEE and The Open Group Standard
126 is the referee document. The original Standard can be obtained online
127 at http://www.unix.org/online.html .
128 Any typographical or formatting errors that appear in this page are
130 most likely to have been introduced during the conversion of the source
131 files to man page format. To report such errors, see https://www.ker‐
132 nel.org/doc/man-pages/reporting_bugs.html .
133IEEE/The Open Group 2013 EXEC(1P)